Heater for enclosed spaces

ABSTRACT

A heater for enclosed spaces includes a casing which is easily installed in a cabinet having a rectangular cutout in one wall thereof. The casing houses a removable sealed combustion chamber assembly having a heat fin positioned behind the actual walls which define the combustion chamber, but in heat-conducting and radiant-heat-absorbing relation therewith. An interior heat shield in the casing surrounds the upper portion of the combustion chamber assembly so that the temperature of the outer walls on the casing does not become excessive, thus enabling those walls to be positioned next to wood and other conventional construction material. A removable airdrop is connected to the backwall of the casing for diverting combustion air from an inlet pipe to the inlet duct leading to the combustion chamber. The airdrop also conveys the flue gases into a flue pipe located within the inlet pipe. The flue pipe and inlet pipe connect with a vent cap which projects only a slight distance beyond the outer wall of the enclosed space. The vent cap enables the burner in the combustion chamber to operate under a wide variety of wind velocity conditions, from a slight wind to a high-velocity wind. Thus, the heater is ideally suited for use in over-the-road vehicles such as trailers.

United States Patent ABSTRACT: A heater for enclosed spaces includes a casing which is easily installed in a cabinet having a rectangular cutout in one wall thereof. The casing houses a removable sealed combustion chamber assembly having a heat fin positioned behind the actual walls which define the combustion chamber, but in heat-conducting and radiant-heat-absorbing relation therewith. An interior heat shield in the casing surrounds the upper portion of the combustion chamber assembly so that the temperature of the outer walls on the casing does not become excessive, thus enabling those walls to be positioned next to wood and other conventional construction material. A removable airdrop is connected to the backwall of the casing for diverting combustion air from an inlet pipe to the inlet duct leading to the combustion chamber. The airdrop also conveys the flue gases into a flue pipe located within the inlet pipe. The flue pipe and inlet pipe connect with a vent cap which projects only a slight distance beyond the outer wall of the enclosed space. The vent cap enables the burner in the combustion chamber to operate under a wide variety of wind velocity conditions, from a slight wind to a high-velocity wind. Thus, the heater is ideally suited for use in overthe-road vehicles such as trailers.

[72] inventor RalphR.Hodges Belleville, Ill. [211 App]. No. 15,684 [22] Filed 'Mar.2, 1970 [45] Patented Dec.21, 1971 [73] Assignee Empire Stove Company Belleville, 111.

[ 54] HEATER FOR ENCLOSED SPACES 16 Claims, 10 Drawing Figs.

[52] U.S.Cl 126/85 B, 126/116 B, 126/307 R [51] 1nt.Cl F24h 3/00, F23j 11/00 [50] Field of Search 126/85,85 8,90,91, 110,11013,116,116B,307

[56] References Cited UNITED STATES PATENTS 3,056,397 10/1962 Little 126/85 B 2,964,034 12/1960 NordholtetaL. 126/1108 3,410,193 11/1968 Clark 126/8513X 2,974,650 3/1961 McCorquodale 126/85 BUX 3,136,309 6/1964 Martz 126/85 B 3,496,927 2/1970 De Werth et a1 126/85 B 32 [L It? T c e l l, l n gl; 5 "1: u I r- I I 54 l ;l l 66 h H s: I i i 5, M l ll 1 85H 34 1/1] 88- .l

92 lfl I 4 jflj l| l r --.u:1.... lT 7; l I l s l= 30 I I PATENTED 0am m SHEET 2 UP 3 3y W H69 M4 M4 m2 HEATER FOR ENCLOSED SPACES BACKGROUND or THE INVENTION This invention relates in general to heaters and more particularly to heaters for enclosed spaces.

Trailers and other recreational vehicles must be equipped with some sort of heating devices in order to be useful the year around. Since most recreational vehicles carry a bottled combustible gas for cooking purposes, it is logical to use the same fuel source for heating the interior of the vehicle also, and heretofore this has been done with limited success.

Vehicular heaters of current construction, however, are quite bulky and consume valuable space within the interior of the vehicle where space is at a premium. This bulkiness is due to a large measure to the desire to isolate the combustion chamber of the heater as much as possible from the surrounding portions of the vehicle in order to reduce the risk of a fire. Moreover, heaters of current construction are difficult to install, and require special brackets and mountings in the vehicle. Once installed they are difficult to service.

Most heaters of current construction which utilize the sealed combustion chamber principle employ an airdrop for supplying combustion air to the lower end of the combustion chamber. These airdrops are positioned vertically and often receive too much heat from the remaining portion of the heater. As a result the combustion air resists downward flow through the airdrop and this adversely affects the efficiency and operation of the burner in the sealed combustion chamber.

I Also many heaters of current construction which employ the sealed combustion chamber principle utilize vent caps which are flush with the exterior of the vehicles. When the wind across these vent caps reaches a critical velocity a blocked vent effect is created, which extinguishes the flame in the combustion chamber. Other vent caps of current construction protrude considerably beyond the outer surface of the vehicle, and while they are not susceptible to the blocked vent effect, they present a hazard for people walking near the vehicle. The projection of this type of end cap also renders the vent cap susceptible to damage as the vehicle is moved.

OBJECTS OF THE INVENTION One of the principal objects of the invention is to provide a highly compact heater for heating enclosed living spaces. Another object is to provide a heater which is easily installed in a simple and compact cabinet constructed from wood or other conventional construction materials. A further object is to provide a heater which is ideally suited for installation in over-the-road vehicles such as trailers, campers, and other recreational vehicles. An additional object is to provide a heater having a sealed combustion chamber and a vet cap which protrudes only a slight distance beyond the exterior surface of the wall on which the vent cap is mounted. Still another object is to provide a heater of the type stated with a vent cap which allows free circulation of air through the heaters combustion chamber, even when the vent cap is subjected to slight or high wind velocities. Yet another object is to provide a heater which is simple in construction and easily serviced. An additional object is to provide a heater of the type stated with an airdrop which does not significantly impede the flow of combustion air to the heater's combustion chamber. These and other objects and advantages will become apparent hereinafter.

SUMMARY OF THE INVENTION The present invention is embodied in a heater including a casing having walls defining a combustion chamber therein. The walls have a fin spaced therefrom, but in heat-conducting relation therewith. The invention is also embodied in a heater having a casing wall on which a removable airdrop is mounted. A heater having a vent cap which for the most part is recessed into a wall also forms part of the invention. The invention also consists in the parts and in the arrangements and combinations of parts hereinafter described and claimed.

DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form part of the specification and wherein like numerals refer to like parts wherever they occur:

FIG. I is a perspective view of the heater of the present invention mounted in a cabinet shown partially broken away and in section;

FIG. 2 is an exploded perspective view of the heater;

FIG. 3 is a front elevational view showing the interior of the heater casing;

FIG. 4 is a rear elevational view of the heater casing show ing the airdrop mounted thereon;

FIGS. 5 and 6 are sectional views taken along lines 5-5 and 6-6, respectively, of FIG. 3;

FIG. 7 is an elevational view of a vent cap forming part of the present invention;

FIGS. 8 and 9 are sectional views taken along lines 8-8 and 9-9, respectively, of FIG. 7; and

FIG. 10 is a sectional view taken along lines 10-10 of FIG. 3 and showing the expansion clips used to hold the heater casing in the wall.

DETAILED DESCRIPTION Referring now in detail to the drawings, 2 designates a heater which is adapted to warm the air within an enclosed space 4 (FIG. 1) to which the front of the heater 2 is exposed. The enclosed space 4 is bounded on one side by an outer wall 6 having a cabinet 8 constructed against it. The heater 2 is installed in and for the most part is enclosed by the cabinet 8. In particular, it is recessed into a front panel 10 of cabinet 8, the wall 10 having a rectangular opening 12 sized for reception of a component of the heater 8. The enclosed space 4 is normally the interior of over-the-road vehicle such as a trailer or other recreational vehicle, but it may also be the room of a building.

The heater 2 includes a casing 14 which slides into the cabinet 8 (FIG. 1) through the rectangular opening 12 in the front panel 10 thereof. The casing 14 includes a pair of sidewalls 16 which are connected across their upper and lower ends by top and bottom walls 18 and 20, (FIG. 5) respectively. At their rear margins the walls l6, l8 and 20 are formed integral with and merge into a backwall 22 (FIG. 4) which extends across and closes the back of the casing 14. The front of the casing 14 remains open (FIG. 3) to provide access to the interior thereof.

The top wall 18 of the casing 14 is inclined downwardly at a slight angle to the horizontal and underlies a heat shield 24 (FIGS. 1 and 5) having side flanges 26 which extend downwardly along and are spot welded to the sidewalls 16. The heat shield 24 is spaced from the inclined top wall 18 and projects horizontally a considerable distance beyond the backwall 22.

At their forward ends the heat shield 24 and the sidewalls 116 turn outwardly in the formation of mounting flanges 28 (FIGS. 5 and 6) which project beyond the margins of the opening 12 and abut against the exposed face on the front panel 10 when the casing 14 is fully inserted in the cabinet 8. The flanges 28 on the sidewalls 16 have guide lips 30 projecting forwardly from them, whereas at the upper end of the casing 14 the top wall 18 projects forwardly beyond the mounting flange 28 of the heat shield 24 and it turns upwardly and then backwardly in the formation of a retention lip 32. The front of the casing 14 is normally covered by a removable grill 34, (FIGS. 1 and 2) the upper end of which fits over and engages the retention lip on the top wall 18. The sides of the grill 34 turn rearwardly and overlie the guide lips 30 which prevent lateral movement of the grill 34. The lower end of the grill 34 also turns rearwardly and is frictionally engaged by a securing lip 35 formed integral with the bottom wall 20 on the casing 14. Thus, when the casing 14 is installed in the cabinet 8 the only portion of the heater 2 which is visible from the enclosed space 4 is the grill 34.

The casing 14 is affixed to the cabinet 8 by expansion clips 36 (FIGS. 1 and 10) which are expanded by screws 38 extending through the mounting flanges 28, on the sidewalls 16. Actually, the screws 38 collapse the clips 36 (FIG. 10) along the longitudinal axes of the screws 38 and in so doing expand the clips 36 laterally, causing them to lodge between the sidewalls 16 and the adjacent edges of the opening 12 in the front panel 10. Thus, the expansion clips 36 both secure the casing 14 in the cabinet 8 and furthermore space the sidewalls 16 from the edges of the opening 12 in the front panel 10 so that heat from the walls 16 is not conducted to the front panel 10. The expansion clips 36 are more fully described in the application of Ralph R. Hodges, Ser. No. 827,539, filed May 26, I969, and entitled EXPANSION CLIP AND METHOD OF IN- STALLING RECESS FIXTURES WITH SUCI-I CLIPS.

The casing 14 further includes an interior heat shield 40 (FIGS. 2, and 6) having side panels 42 which are spaced inwardly from the sidewalls l6 and at their forward ends turn outwardly where they are spot welded to the front faces of the mounting flanges 28. The heat shield 40 also includes a back panel 44 and a top panel 46 which are spaced inwardly from the backwall 22 and top wall 18, respectively.

Each side panel 42 has a pair of reinforced tabs 48 (FIGS. 3 and 6) projecting inwardly into the interior of the casing 14, and those tabs 48 have a combustion chamber assembly 50 bolted thereto so that the combustion chamber assembly 50 is in effect suspended within the'interior of the casing 14. The combustion chamber assembly 50 includes (FIGS. 3, 5 and 6) a back wall 52 and a front wall 54 both of which possess a hol lowed-out configuration and are joined together to form a combustion chamber 56. The lower end of the combustion chamber 56 is closed by a cover plate 57 which overlies and is fastened to the walls 52 and 54 by means of screws 58. Access to the interior of the combustion chamber 56 is gained by removing the screws 58, and withdrawing the cover plate 57. The screws 58 also compress a gasket 59 (FIG. 5) between the overlapping portions of the cover plate 57 and the walls 52 and 54.

The combustion chamber. assembly 50 further includes a heat fin 60 (FIGS. 2, 5 and 6) which is positioned between the back panel 44 of the interior heat shield 40 and the back wall 52 of the combustion chamber 56. At its ends the fin 60 has connecting flanges 62 which extend forwardly and are spot welded to the sides of the backwall 52 so that heat from the combustion chamber 56 is conducted through the flanges 62 to the fin 60.

Near its lower end the backwall 52 has an inlet duct 64 (FIG. 5) connected to it and that duct opens into the combustion chamber 56 for delivering combustion air thereto. At its upper end the backwall 52 has a discharge duct 66 connected to it, and that duct likewise opens into the chamber 56 for allowing the products of combustion to escape from the chamber 58. Thus, the combustion chamber 56 is of the sealed variety.

The duct 64 projects rearwardly beyond the heat fins 60 as well as beyond the back panel 44 of the interior heat shield 40 and terminates adjacent to but slightly inwardly from the backwall 22 which is apertured to expose the end of the duct 66 therethrough. The discharge duct 66 on the other hand projects completely through and is snugly embraced by the heat fin 66 so that heat from the flue gases in the duct 66 is conducted to the heat fin 60. Beyond the heat fin 60 the duct 66 projects through the back panel 44 of the heat shield 40, and further through the backwall 22 which is apertured to receive it. Between the ends of the ducts 64 and 66 the backwall 22 is provided witha shallow recess 72 (FIGS. 5 and 6) which opens rearwardly, and appears as an embossment on the opposite or forward side of the wall 22.

Mounted within and extending completely across the lower part of the combustion chamber 56 is a burner 74, (FIGS. 5 and 6) access to which is gained by removing the cover plate 57 of the combustion chamber assembly 50. The burner 74 draws combustion air from within the chamber 56 and is supplied with a combustible gas through a manifold 76 which is connected thereto at its one end and projects through the side of the backwall 52 at its opposite end. Near the center of the burner 74 the cover plate 57 is recessed inwardly and fitted with an inclined mounting plate 78 (FIGS. 3 and 6) through which a pilot nozzle 80 and a thermocouple junction 82 project. The pilot nozzle 80 is positioned within the chamber 56 near the gas orifices in the burner 74, while the thermocouple junction 82 is positioned next to the pilot nozzle 80. Immediately above the nozzle 80 the front wall 54 has an access opening 84 which is normally covered by window 86 formed from mica or some other suitable transparent material and an overlying cover plate 88. The window 86 and plate 88 are held in place by wingnuts 90 which thread over studs 92 projecting from the front wall 54.

At its lower end the manifold 76 is threaded into a thermostat regulator 94 (FIGS. 2 and 3) which is in turn connected to an adjoining control valve 96. The combustible gas is furnished to the heater through a gasline 98 which threads into the control valve 96. The pilot nozzle 80 is connected to the valve 96 through a gasline 97, and gas will flow through this line only when the thermocouple junction 86 is heated or the solenoid valve to which it is connected is temporarily bypassed in the conventional manner. The thermostat regulator 94 is of the hydraulically operated variety and includes a thermostat bulb 100 which is confined in a pair of mounting tabs 102 (FIGS. 3 and 5) projecting outwardly from the bottom wall 20 of the casing 14 beneath the securing lip 35. The thermostat regulator 94 also includes a control knob 104 which is exposed through an opening in the lower right-hand comer of the grill 34.

Turning now to the back of the casing 14, an airdrop (FIGS. 4-6) is bolted against that portion of the backwall 22 into which the shallow recess 72 is formed. The airdrop 110 includes an inner wall 112 which is provided slightly inwardly from its peripheral margin with a shallow recess 114 (FIG. 2) identical in configuration to the recess 72. The recess 114 however opens toward the recess 72 so that a space (FIG. 5) exists between the walls 22 and 112 in the area between and slightly beyond the ends of the ducts 64 and 66. Indeed, the inner wall 112 only abuts the backwall 22 along a relatively narrow peripheral rim through which self-tapping screws 116 extend for securing the airdrop 110 to the backwall 22 of the casing 14. Thus, the transfer of heat between the backwall 22 and of the airdrop 110 is minimized by the presence of the opposed recesses 72 and 114. At its lower end the inner wall 112 is provided with a forwardly projecting circular boss 118 (FIGS. 5 and 6) which fits into the lower aperture in the backwall 22 through which the end of the inlet duct 64 is exposed. The forward end of the boss 118 turns inwardly upon itself in the formation of a circular internal lip 119 which defines an aperture sized to receive the end of the inlet duct 64 leading into the combustion chamber 56.

At its upper end the airdrop 110 is fitted with a tapered collar 120 (FIG. 5) having one end flared outwardly and spot welded to the inner wall 112 in alignment with the end of the discharge duct 66 which it snugly receives.

In addition to the inner wall 112, the airdrop 110 includes an outer wall 122 which for the most part is spaced outwardly from the inner wall 112, but is attached at its sides and ends to the sides and ends of the inner wall 112 so as to form an air supply channel 123 through the airdrop 110. At its upper end the outer wall 124 has an outwardly flared circular lip 124 which is spaced radially from and is concentric to the rear end of the collar 120. Thus, the annular void between the circular lip 124 and the end of the collar 120 forms the entrance into the air supply channel 123 within the airdrop 110.

The circular lip 124 on the airdrop 110 is tapered slightly and fits snugly into the end of an inlet pipe 126 which extends rearwardly toward the outer wall 6 of the enclosed space 4. Similarly, the end of the collar 120 fits snugly within a flue pipe 128 and also extends rearwardly through the inlet pipe 126. Both of the pipes 126 and 128 terminate at a vent cap 129 (FIGS. 1, 2 and 7-9) which is recessed into the outer wall 6 of the enclosed space 4.

The vent cap 129 includes an inlet box 130 which is set into the outer wall 6, and connects with the inlet pipe 126. In particular, the inlet box 130 has a recessed center portion 132 (FIGS. 8 and 9) which is surrounded by a mounting flange 134. The center portion 132 fits into a hole 135 (FIG. 1) formed in the wall 6, whereas the flange 134 projects beyond the margins of the hole 135 and overlies the outer surface of the wall 6. The flange 134 and likewise the entire inlet box 138 are held to the wall 6 by screws 136. The recessed portion 132 merges into a tapered circular lip 138 which projects toward the casing 14 and fits snugly into the rear end of the inlet pipe 126 just as the circular lip 124 on the airdrop 1 10 fits into the forward end of the inlet pipe 126.

On the other hand, the rear end of the flue pipe 128 connects with an end cap 140 which also forms part of the vent cap 129 and for the most part is disposed within the recessed portion 132 of the inlet box 130. More specifically, the end cap 140 includes (FIGS. 2, 8 and 9) a pair of side flanges 142 having mounting tabs 144 which are secured against the mounting flanges 134 of the inlet by box 130 by the screws 136. The mounting tabs 144 position the side flanges 142 slightly outwardly from the mounting flange 134 (FIGS. 8 and 9) of the inlet box so that combustion air is free to pass between the two and enter the recessed portion 132 of the inlet box 130. The side flanges 142 at their inner margins merge into a depressed center portion 146 which extends into the recessed portion 132 of the flue box 130 but is spaced inwardly from the walls thereof so as not to inhibit the flow of combustion air through the recessed portion 132 toward the inlet pipe 126. The depressed portion 146 includes a cross wall 148 which extends through the interior of the recessed portion 132 and at its upper end merges into an oblique wall 150. The oblique wall 150 in turn merges into a top flange 152 which is positioned coplanar to the side flanges 142 and is likewise disposed outwardly from the mounting flange 134 at the top of the inlet box 130. The cross wall 148 is centrally provided with a tapered collar 154 which projects through the circular lip 138 of the inlet box 130 and fits snugly into the rear end of the flue pipe 128, just as the collar 120 fits into the opposite end of the pipe 128. The collar 154 projects completely through the cross wall 148 so that the flue gases from the pipe 128 are carried beyond the wall 148 into the confines of the depressed portion 146.

Outwardly beyond the cross wall 148 the depressed portion 146 is transversed by a defecting wall 156, the outer surface of which is flush with the side and top flanges 142 and 152 and furthermore continuous with the side flanges 142. The defecting wall 156 actually consists of two plates spaced about onequarter inch apart with the lower ends of the plates canted inwardly to form a slight lip 158 projecting into the depressed portion 146. The inner of the two plates deflects the flue gases from the flue pipe 128 generally upwardly toward the oblique wall 150, while the outer of the two plates being spaced from the inner plate remains relatively cool and serves as a protective shield across the inner plate.

The heater 2 is supplied with the combustion chamber assembly 50 including the burner 74 and valves 94 and 96 installed in the casing 14 and the airdrop 110 attached to the back of the casing 14 and connected with intake and discharge ducts 64 and 66 on the combustion chamber assembly 50. The inlet pipe 126, flue pipe 128, inlet box 130 and end cap 140 are all furnished individually, but in the same packing container.

To install the heater 2, the cabinet 8 (FIG. 1) with the rectangular opening 12 in its front panel 10 is constructed adjacent the outer wall 6 and an opening is cut in the outer wall 6 at the proper location to receive the inlet box 130 of the vent cap 129. Thereupon, the casing 14 is inserted into the opening 12 in the cabinet 8 until the mounting flanges 28 abut against the outer face of the front panel 10. At that time the screws 38 are tightened, causing (H0. 16) the expansion clips 36 to expand laterally and lodge between the edges of the opening 12 and the sidewalls 16 on the casing 14. This secures the casing 14 firmly in the cabinet 8 and furthermore spaces its sidewalls 16 from the margins of the opening 12.

With the casing secured in the cabinet 8, the inlet and flue pipes 126 and 128 are cut to the proper length and then installed on the circular lip 124 and collar 120, respectively, of the airdrop through the opening cut in the outer wall 6. Next the circular lip 138 and the inlet box 130 is fitted into the rearmost end of the inlet pipe 126, and the inlet box 138 is secured against the wall 6 by driving at least one screw 136 through its mounting flange 134 at a location thereon which is not normally covered by the flanges 142 and 152 on the end cap 140. The screw 136 of course threads into the outer wall 6 and thereby holds the inlet box 1311 temporarily in place. The inlet box 138 should be installed such that the inlet pipe 126 is pitched downwardly toward it at a slight angle so that any moisture which finds its way into the pipe 126 will drain toward the inlet box 130 and not into the airdrop 118.

Once the inlet box 130 is temporarily set in place in the wall 6, the collar 154 on the end cap 140 is fitted into the rearmost end of the flue pipe 128, in which case the depressed portion 146 will be disposed within the recessed portion 132 of the inlet box 130. Thereafter the remaining screws 136 are passed through the mounting tabs 144 on the end cap 140 and the underlying mounting flange 134 on the inlet box 138 and are driven into the wall 6 so as to permanently secure the vent cap 129 as well as the pipes 126 and 128 permanently in place. Since the inlet pipe 126 slopes away from the airdrop 118, so will the flue pipe 128 and water will not drain into combustion chamber 56.

To light the heater 2, the window 86 and cover plate 88 are lifted away from the access opening 84 and the control valve 96 is set to override the thermocouple junction 82 and direct the combustible gas through the line 99 to the pilot nozzle 80. Thereupon, the burning head of a lighted match is inserted through the access opening 84, and since that opening 84 is positioned directly above the pilot nozzle 88, the gas from the nozzle 88 will ignite. The flange at the pilot nozzle 88, heats the thermocouple junction 82, and once that junction reaches the prescribed temperature the pilot flame remains selfsustaining.

After the pilot is lit the control valve 96 is set so that gas is directed to the thermostat regulator 94 which in turn discharges the gas into the manifold 76. From the manifold 76 the gas enters the burner 74 where it is mixed with combustion air from the lower end of the combustion chamber 56, forming a combustible mixture which is discharged upwardly through the orifices in the burner 74. The combustible mixture is, of course, ignited by the flame at the pilot nozzle 88, creating a flame along the entire length of the burner 74 and combustion chamber 56. This flame sets up convention currents in the combustion chamber 56 and heats the baclt and front walls 52 and 54 of the combustion chamber assembly 50.

The heated products of combustion rise through the combustion chamber 56 and induce convention currents therein. At the upper end of the chamber 56 the products of combustion enter the discharge duct 66 and flow into the flue pipe 128 after passing through the collar 1211 at the upper end of the airdrop 110. The flue pipe 128 discharges the products of combustion against the deflecting wall 156 of the end cap 148 which directs it upwardly through the depressed portion 146 of the end cap 140. The rising flue gases pass along the oblique wall 150 in the end cap 140, at the end of which they leave the vent cap 129 and are vented to the atmosphere.

The convection currents induced by the flame at the burner 74 draw fresh combustion air into the bottom of the combustion chamber 56 through the inlet duct 64 which is connected to the air supply channel 123 in the airdrop 118. The supply channel 123 in turn receives air from the inlet pipe 126 which is connected to the recessed portion 132 of the inlet box 130. The combustionair enters the recessed portion 132 of the inlet box 130 below the lip 158 on the end cap 140 and between the flanges 142 and 152 on the end cap 140 and the underlying mounting flanges 134 on the inlet box 130.

The flow of combustion air into the inlet box 130 and inlet pipe 126 and the flow of flue gases out of the flue pipe 128 and end cap 140 remains continuous even when wind exists across the outer wall 6, and no blocked vent effect occurs irrespective of whether the wind velocity is slight or great. The flow through the combustion chamber 58 remains unaffected by the wind velocity across the inlet box 130 and end cap 140 due to the balance bias created by locating the end cap 140 in a turbulent area next to the wall 6 and by allowing ample relief areas between the flanges 142 and 152 on one hand and the mounting flange 134 on the other. This enables wind or turbulent air to enter the inlet'box 130 and create a pressure differential across the combustion chamber 56.

In a balanced vent system such as a true flush vent or an extended concentric vent, the only force available to move air into the air inlet and out the flue outlet is the heat developed by the burner. This creates a very slight negative pressure in the flue outlet and a very slight positive pressure in the air inlet. When a balanced vent operates in wind conditions it does not maintain perfect balance but swings across zero, allowing flue outlet pressures and inversely inlet pressures to fluctuate very slightly positive or negative. A slight positive pressure in the flue outlet can overpower the slight negative pressure due to burner heat and thus cause a blocked flue condition, and this will result in a burner outage. The vent cap 129 avoids the blocked flue condition due to the form and location of air inlet apertures and flue outlet apertures which allows the flue outlet pressure to swing from zero to slightly negative and the air inlet pressure inversely to swing from zero to slightly positive with neither being able to cross the zero line. This effectively prevents a reversed or blocked airflow condition which could cause outage.

Thus, the vent cap 129 avoids the blocked vent effect associated with conventional flush-type vent caps when they are subjected to gentle winds. The vent cap 129 is therefore ideally suited for use on trailers and other recreational vehicles designed for over-the-road use.

Since the vent cap 129 projects only'a very short distance beyond the;outer surface of the wall 6 it does not present a hazard to one walking close to the wall 6. This is in contrast to many conventional vent caps which project considerably beyond the wall into which they are fitted. The double plate construction of the deflecting wall 156 in the end cap 140 prevents that exposed surface from reaching high temperatures, and accordingly the risk of someone being burned by the end cap 129. is minimized.

The flue gases, of course, heat the flue pipe 128 into a relatively high temperature, but that pipe is disposed entirely within and completely shielded by the inlet pipe 126 so that no fire hazard exists. The upper heat shield 24 which extends partially over the pipes 126 and 128 further reduces the danger.

By reason of the opposed recesses 72 and 114 on the back wall 22 of the casing 14 and on the inner wall 112 of the airdrop 110, respectively, the airdrop 110 for the most part is spaced away from the backwall 22 of the casing 14. This insulates the airdrop 110 from the backwall 22 so that the air within it remains relatively cool and at a constant temperature. Consequently, it has little tendency to resist the normal conventive flow and flow downwardly into the inlet duct 64 leading to the combustion chamber 56.

Turning now to the interior of the casing 14, the back and front heated walls 52 and 54 of the combustion chamber assembly 50 heat the air surrounding them and causes that air to rise, thereby inducing convection currents through the casing 14. The heated air rising from the walls 52 and 54 is deflected forwardly and out of the casing 14 by the inclined top wall 18. Since the heat fin 60 is connected to the backwall 52 by the connecting flanges 62 at the ends thereof, considerable heat is conducted to it through the flanges 62. More heat is conducted from the discharge duct 66 to the fin 60 at the location where the fin 60 embraces the duct 66. The heat fin 60 receives still more heat by way of radiation from the heated backwall 52. inasmuch as the tin 60 extends vertically through the casing and is exposed on both sides to the airstream induced through the casing 14, it dissipates heat into that airstream and enhances the efficiency of the heater 2.

The side panels 42 and back panel 44 of the interior heat shield 40, being respectively spaced from the sidewalls 16 and backwall 22 of the casing 14, are also exposed on both faces to the airstream passing through the casing 14 and further serve to impart heat to that airstream and increase the efficiency of the heat 2 thereby. In this connection, it should be noted that the front ends of the top wall 22 and top panel 46 in the casing 14 are spaced apart at their forward ends so that the heated air between them discharges into the enclosed space 4 through the drill 34. The panels 42, 44 and 46 on the heat shield 40 receive heat primarily by radiation and by reason of this fact they shield those portions of outer walls 16, 18 and 22 which would normally be exposed to the heat of the backwall 52 on the combustion chamber assembly 50. Consequently, the sidewall 16, bottom wall 20, and backwall 22 which form the outwardly presented surface of the casing do not reach high temperatures and can be used against wood and other conventional construction materials without danger. The upper heat shield 24 provides additional protection across the top of the casing 14 and does not reach high temperatures either. Therefore, it too can be used against wood and most other construction materials.

Access to the interior of the casing 14 is gained by merely pulling the lower end of the grill away from the securing lip 35 on the bottom wall 20 and then lifting it upwardly off of the retention lip 32 on the top wall 18. The entire combustion chamber assembly 50 is positioned in the casing 14 by only four screws at the tabs 48 and can be easily withdrawn from the casing 14 by removing those screws. Removal of the cover plate 57 on the combustion chamber assembly 50 affords access to the lower end of the combustion chamber 56 for servicing the burner 74 or the pilot nozzle and thermocouple junction 82. Thus, the heater 2 is easily serviced.

If the natural convection through the casing 14 does not supply enough heated air, a blower may be mounted on the bottom wall 20 beneath the combustion chamber assembly 50 and opposite to the valve 96. Such a blower should be oriented to force air upwardly between the backwall 52 the heat fin 60 of the combustion chamber assembly 50.

This invention is intended to cover all changes and modifications of the example of the invention herein chosen for purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

l. A heater comprising a casing including a pair of sidewalls, a backwall, a top wall, and an interior heat shield, the heat shield having side panels spaced inwardly from the sidewalls, a back panel spaced inwardly from the backwall, and a top panel spaced inwardly from the top wall; combustion chamber walls mounted in the casing and attached to the interior heat shield, the combustion chamber walls defining a sealed combustion chamber; a burner in the combustion chamber; inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air thereto and exhausting flue gases therefrom; and a fin mounted in the casing in outwardly spaced relation to at least one of the combustion chamber walls, the tin being in heat-conducting relation with respect to the combustion chamber walls so that the heat generated in the combustion chamber is transferred to the fin. whereby air circulating through the casing will be heated by the combustion chamber walls and the tin.

2. A heater according to claim 1 wherein the tin has a flange along at least one of its margins, the flange being connected to the one of the combustion chamber walls for conducting heat to the fin.

3. A heater according to claim 1 wherein the side panels of the interior heat shield are provided with inwardly projecting mounting tabs and the combustion chamber walls are detachably connected to the tabs.

4. A heater according to claim 1 wherein the top and backwalls of the casing are connected; wherein the top and baclt panels of the interior heat shield are connected; wherein a continuous channel exists between the back and top walls and the back and top panels so'that the heat from the combustion chamber will induce air to flow through the channel and be discharged between the forward ends of the top wall and top panel.

5. A heater according to claim 4 wherein the top wall and top panel are inclined downwardly toward the backwall and panel so that the heated air will be deflected out of the front of the casing.

6. A heater comprising a casing having a wall provided with a shallow recess; combustion chamber walls defining a sealed combustion chamber in the casing; a burner in the combustion chamber; inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air to and for exhausting the products of combustion from the combustion chamber; and an airdrop detachably connected to the casing wall, the airdrop defining an air supply channel and including an inner wall presented adjacent to the outer surface of the casing wall and having a shallow recess positioned opposite the shallow recess in the casing wall such that the casing wall and the inner wall are for the most part spaced apart to minimize transfer of heat from the casing to air within the airdrop, an outer wall, a collar which extends through the air supply channel and engages the discharge duct leading from the combustion chamber, an inlet port formed in the outer wall and exposing the collar, and an outlet port formed in the inner wall below the inlet port and engaged with the inlet duct leading to the combustion chamber.

7. A heater comprising a casing having a wall, combustion chamber walls defining a sealed combustion chamber in the casing, a burner in the combustion chamber, inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air to and for exhausting the products of combustion from the combustion chamber, an airdrop detachably connected to the casing wall, the airdrop defining an air supply channel and including an inner wall presented adjacent to the casing wall, an outer wall, a collar extending through the air supply channel and engaged with the discharge duct leading from the combustion chamber, a inlet port formed in the outer wall and exposing the collar, and an outlet port formed in the inner wall below the inlet port, and comprising an embossment extending outwardly from the inner wall and through the casing wall, and an inwardly turned lip at the outer end of the embossment, the lip defining an aperture which snugly receives the inlet duct leading to the combustion chamber.

8. A heater according to claim 7 and further characterized by an inlet pipe connected with the inlet port on the airdrop, a flue pipe connected with the collar and disposed within inlet pipe, and a vent cap connected to the ends of the flue and inlet pipes for introducing fresh air into the inlet pipe and for exhausting the products of combustion from the flue pipe.

9. A heater for heating an enclosed space defined in part by an outer wall, said heater comprising a casing, means defining sealed combustion chamber in the casing, supply and discharge conducts leading to and from the combustion chamber for supplying combustion air to and exhausting the products of combustion from the combustion chamber, the portion of the discharge conduct located remote from the combustion chamber extending through the outer wall and being disposed within the supply conduct, and a vent cap mounted in the outer wall for introducing combustion air into the supply conduct and for exhausting the products of combustion from the discharge conduct, the vent cap comprising lllll an inlet box recessed into the outer wall and forming a cavity which opens outwardly from the wall and is exposed to the atmosphere, the inner end of the inlet box being connected with the supply conduit so that air for combustion is drawn into the supply conduit from the inlet box, an end cap disposed within the inlet box cavity and having walls spaced from the surfaces defining the cavity of the inlet box, the end cap being connected with the discharge conduit at its inner end and opening outwardly into the atmosphere at its outer end so that the products of combustion from the discharge duct are discharged into the atmosphere through the end cap, walls of the end cap projecting outwardly slightly beyond the outer margins of the inlet box cavity, the end cap further having flanges connected to the outwardly projecting walls thereof, the flanges extending laterally beyond the margins of the inlet box cavity and being spaced outwardly from those margins so that air for combustion can enter the inlet box cavity from behind the end cap flanges.

10. A heater according to claim wherein the end cap further comprises a deflecting wall extending between two of the walls thereof which project beyond the margins of the inlet box cavity and being spaced outwardly from the discharge conduct so that the flue gases are deflected away from the incoming combustion air.

11. A heater according to claim 10 wherein the end cap opens upwardly but not laterally whereby the flue gases are exhausted upwardly.

12. A heater according to claim 111 wherein one of the walls of the end cap is a cross wall which extends through the cavity of the inlet box behind the deflecting wall, and another is an oblique wall connected to the cross wall and terminating above and in spaced relation to the upper margin of the deflecting wall.

113. A heater according to claim lll wherein the inlet box includes a mounting flange which surrounds the cavity and overlies the outer surface of the outer wall, wherein the flanges of the end cap are located at the sides thereof and are spaced outwardly from the mounting flanges, whereby combustion air can enter the cavity between the end cap flanges and mounting flanges.

M. A heater according to claim 13 wherein one of the walls of the end cap is a cross wall extending across the cavity of the inlet box behind the deflecting wall and another is an oblique wall connected to the cross wall and terminating above and in spaced relation to the upper margin of the deflecting wall; and wherein the oblique wall is connected to a top flange which is located in outwardly spaced relation to the mounting flange on the inlet box.

15. A heater comprising a casing having a backwall and sidewalls projecting away from the backwall, a combustion chamber wall mounted in the casing and defining a sealed combustion chamber, the combustion chamber walls being presented opposite to and spaced outwardly from the casing backwall and the casing being unobstructed at the top and bottom of the combustion chamber wall so that air flows between the bacltwall and the combustion chamber wall, an inlet duct connected to the combustion chamber wall near the lower end of the combustion chamber and communicating with the combustion chamber for admitting air to the com bustion chamber, an outlet duct connected to the combustion chamber wall near the upper end of the combustion chamber and communicating with the combustion chamber for exhausting the products of combustion from the combustion chamber, the inlet and outlet ducts projecting through the backwall in vertically spaced relation to one another with the outlet duct being positioned above the inlet duct, a tin interposed between and spaced from both the casing back wall and the combustion chamber wall, and connecting flanges extending between the fin and the combustion chamber wall so that heat from the combustion chamber is conducted through the connecting flanges to the tin, the connecting flanges being spaced inwardly from the casing sidewall, whereby air circulating through the casing will be heated by the combustio chamber wall and the tin.

3 62 8 2 1 11 16. A heater according to claim 21 wherein the discharge duct extends through and is embraced by the fin whereby the heat from the flue gases is transferred to the fin.

* i i i UNHED STATES PATENT @FEFMZE QERTH MATE @F RRE CMN Patent No. 3,628,521 Dated December 21, 197].

Inventor(s) Ralph R. Hodges It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 1,, line 53, "vet" should be "vent",

Col. 8, line 18, "drill" should be "grill'H.

C01. 11, line 1, "21" should be "15".,

Signed and sealed this 30th day of January 1973.,

(SEAL) Attest:

,EDWARD MWFLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM P0-1050 (10-69) USCOMM-DC scam-ps9 US. GOVERNMENT PRINTING OFFICE: I965 0-3fi6-334 

1. A heater comprising a casing including a pair of sidewalls, a backwall, a top wall, and an interior heat shield, the heat shield having side panels spaced inwardly from the sidewalls, a back panel spaced inwardly from the backwall, and a top panel spaced inwardly from the top wall; combustion chamber walls mounted in the casing and attached to the interior heat shield, the combustion chamber walls defining a sealed combustion chamber; a burner in the combustion chamber; inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air thereto and exhausting flue gases therefrom; and a fin mounted in the casing in outwardly spaced relation to at least one of the combustion chamber walls, the fin being in heat-conducting relation with respect to the combustion chamber walls so that the heat generated in the combustion chamber is transferred to the fin, whereby air circulating through the casing will be heated by the combustion chamber walls and the fin.
 2. A heater according to claim 1 wherein the fin has a flange along at least one of its margins, the flange being connected to the one of the combustion chamber walls for conducting heat to the fin.
 3. A heater according to claim 1 wherein the side panels of the interior heat shield are provided with inwardly projecting mounting tabs and the combustion chamber walls are detachably connected to the tabs.
 4. A heater according to claim 1 wherein the top and backwalls of the casing are connected; wherein the top and back panels of the interior heat shield are connected; wherein a continuous channel exists between the back and top walls and the back and top panels so that the heat from the combustion chamber will induce aIr to flow through the channel and be discharged between the forward ends of the top wall and top panel.
 5. A heater according to claim 4 wherein the top wall and top panel are inclined downwardly toward the backwall and panel so that the heated air will be deflected out of the front of the casing.
 6. A heater comprising a casing having a wall provided with a shallow recess; combustion chamber walls defining a sealed combustion chamber in the casing; a burner in the combustion chamber; inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air to and for exhausting the products of combustion from the combustion chamber; and an airdrop detachably connected to the casing wall, the airdrop defining an air supply channel and including an inner wall presented adjacent to the outer surface of the casing wall and having a shallow recess positioned opposite the shallow recess in the casing wall such that the casing wall and the inner wall are for the most part spaced apart to minimize transfer of heat from the casing to air within the airdrop, an outer wall, a collar which extends through the air supply channel and engages the discharge duct leading from the combustion chamber, an inlet port formed in the outer wall and exposing the collar, and an outlet port formed in the inner wall below the inlet port and engaged with the inlet duct leading to the combustion chamber.
 7. A heater comprising a casing having a wall, combustion chamber walls defining a sealed combustion chamber in the casing, a burner in the combustion chamber, inlet and discharge ducts communicating with the combustion chamber through at least one of the combustion chamber walls for supplying combustion air to and for exhausting the products of combustion from the combustion chamber, an airdrop detachably connected to the casing wall, the airdrop defining an air supply channel and including an inner wall presented adjacent to the casing wall, an outer wall, a collar extending through the air supply channel and engaged with the discharge duct leading from the combustion chamber, a inlet port formed in the outer wall and exposing the collar, and an outlet port formed in the inner wall below the inlet port, and comprising an embossment extending outwardly from the inner wall and through the casing wall, and an inwardly turned lip at the outer end of the embossment, the lip defining an aperture which snugly receives the inlet duct leading to the combustion chamber.
 8. A heater according to claim 7 and further characterized by an inlet pipe connected with the inlet port on the airdrop, a flue pipe connected with the collar and disposed within inlet pipe, and a vent cap connected to the ends of the flue and inlet pipes for introducing fresh air into the inlet pipe and for exhausting the products of combustion from the flue pipe.
 9. A heater for heating an enclosed space defined in part by an outer wall, said heater comprising a casing, means defining sealed combustion chamber in the casing, supply and discharge conducts leading to and from the combustion chamber for supplying combustion air to and exhausting the products of combustion from the combustion chamber, the portion of the discharge conduct located remote from the combustion chamber extending through the outer wall and being disposed within the supply conduct, and a vent cap mounted in the outer wall for introducing combustion air into the supply conduct and for exhausting the products of combustion from the discharge conduct, the vent cap comprising an inlet box recessed into the outer wall and forming a cavity which opens outwardly from the wall and is exposed to the atmosphere, the inner end of the inlet box being connected with the supply conduit so that air for combustion is drawn into the supply conduit from the inlet box, an end cap disposed within the inlet box cavity and having walls spaced from the surfaces defining the cavity of the inlet box, the End cap being connected with the discharge conduit at its inner end and opening outwardly into the atmosphere at its outer end so that the products of combustion from the discharge duct are discharged into the atmosphere through the end cap, walls of the end cap projecting outwardly slightly beyond the outer margins of the inlet box cavity, the end cap further having flanges connected to the outwardly projecting walls thereof, the flanges extending laterally beyond the margins of the inlet box cavity and being spaced outwardly from those margins so that air for combustion can enter the inlet box cavity from behind the end cap flanges.
 10. A heater according to claim 9 wherein the end cap further comprises a deflecting wall extending between two of the walls thereof which project beyond the margins of the inlet box cavity and being spaced outwardly from the discharge conduct so that the flue gases are deflected away from the incoming combustion air.
 11. A heater according to claim 10 wherein the end cap opens upwardly but not laterally whereby the flue gases are exhausted upwardly.
 12. A heater according to claim 11 wherein one of the walls of the end cap is a cross wall which extends through the cavity of the inlet box behind the deflecting wall, and another is an oblique wall connected to the cross wall and terminating above and in spaced relation to the upper margin of the deflecting wall.
 13. A heater according to claim 11 wherein the inlet box includes a mounting flange which surrounds the cavity and overlies the outer surface of the outer wall, wherein the flanges of the end cap are located at the sides thereof and are spaced outwardly from the mounting flanges, whereby combustion air can enter the cavity between the end cap flanges and mounting flanges.
 14. A heater according to claim 13 wherein one of the walls of the end cap is a cross wall extending across the cavity of the inlet box behind the deflecting wall and another is an oblique wall connected to the cross wall and terminating above and in spaced relation to the upper margin of the deflecting wall; and wherein the oblique wall is connected to a top flange which is located in outwardly spaced relation to the mounting flange on the inlet box.
 15. A heater comprising a casing having a backwall and sidewalls projecting away from the backwall, a combustion chamber wall mounted in the casing and defining a sealed combustion chamber, the combustion chamber walls being presented opposite to and spaced outwardly from the casing backwall and the casing being unobstructed at the top and bottom of the combustion chamber wall so that air flows between the backwall and the combustion chamber wall, an inlet duct connected to the combustion chamber wall near the lower end of the combustion chamber and communicating with the combustion chamber for admitting air to the combustion chamber, an outlet duct connected to the combustion chamber wall near the upper end of the combustion chamber and communicating with the combustion chamber for exhausting the products of combustion from the combustion chamber, the inlet and outlet ducts projecting through the backwall in vertically spaced relation to one another with the outlet duct being positioned above the inlet duct, a fin interposed between and spaced from both the casing back wall and the combustion chamber wall, and connecting flanges extending between the fin and the combustion chamber wall so that heat from the combustion chamber is conducted through the connecting flanges to the fin, the connecting flanges being spaced inwardly from the casing sidewall, whereby air circulating through the casing will be heated by the combustion chamber wall and the fin.
 16. A heater according to claim 21 wherein the discharge duct extends through and is embraced by the fin whereby the heat from the flue gases is transferred to the fin. 